Gas turbines are used in many fields for driving generators or mobile machines. Here, the energy content of a fuel is used to generate a rotational movement of a turbine rotor. To this end, the fuel is burned in a combustion chamber, air being fed in which has been compressed by an air compressor. Here, the operating medium which is produced in the combustion chamber by the combustion of the fuel and is under high pressure and at high temperature is fed via a turbine unit which is connected behind the combustion chamber and where said operating medium is relieved so as to do work.
Here, in order to generate the rotational movement of the turbine rotor, a number of rotor blades which are usually combined to form blade groups or blade rows are arranged on said turbine rotor. Here, a turbine disk is usually provided for each turbine stage, to which turbine disk the rotor blades are fastened by means of their blade root. In addition, in order to guide the flow of the operating medium in the turbine unit, guide blades which are connected to the turbine housing and are combined to form guide blade rows are usually arranged between adjacent rotor blade rows.
The combustion chamber of the gas turbine can be configured as what is known as an annular combustion chamber, in which a multiplicity of burners which are arranged around the turbine rotor in the circumferential direction open into a common combustion chamber space which is surrounded by a surrounding wall which is resistant to high temperatures. To this end, the combustion chamber in its entirety is configured as an annular structure. Besides a single combustion chamber, a plurality of combustion chambers can also be provided.
The combustion chamber is as a rule adjoined immediately by a first guide blade row of a turbine unit which, together with the immediately following rotor blade row as viewed in the flow direction of the operating medium, forms a first turbine stage of the turbine unit, behind which first turbine stage further turbine stages are usually connected.
In the design of gas turbines of this type, a particularly high degree of efficiency is usually a design target in addition to the power output which can be achieved. Here, an increase in the degree of efficiency can be achieved for thermodynamic reasons in principle by an increase in the outlet temperature, at which the operating medium flows out of the combustion chamber and into the turbine unit. Here, temperatures of approximately from 1200° C. to 1500° C. are aimed for and also achieved for gas turbines of this type.
At high temperatures of this type of the operating medium, however, the components and elements which are exposed to them are exposed to high thermal loadings. In order to protect the turbine disk from contact with hot operating medium and in order to guide cooling air along the side faces of the rotor disk to the rotor blades, sealing plates are usually provided on the turbine disks, which sealing plates are attached to the side faces, which are perpendicular in each case with respect to the turbine axle, such that they extend around circularly.
Here, in each case one sealing plate is usually provided per turbine blade on each side of the turbine disk. Said sealing plates overlap in an imbricated manner and usually have a sealing vane which extends as far as the respectively adjacent guide blade in such a way that a penetration of hot operating medium in the direction of the turbine rotor is avoided.
However, the sealing plates also fulfill further functions. They form firstly the axial fixing of the turbine blades by corresponding fastening elements, and secondly they not only seal the turbine disk against penetration of hot gas from the outside, but also avoid the escape of cooling air which is guided in the interior of the turbine disk and is usually guided further into the turbine blades to cool the latter. A gas turbine in a refinement of this type is known, for example, from EP 1 944 471 A1.
The abovementioned refinement of the turbine disks with sealing plates which overlap in a segmented and imbricated manner is relatively complicated, however. A relatively large number of sealing plates are required, which leads to a comparatively high construction outlay of the turbine disks and therefore of the entire gas turbine. Furthermore, a possibly required repair in the region of the turbine disks can be comparatively complicated as a result of this construction.
In addition, US 2008/0181767 A1 has disclosed a securing means for sealing sheets of turbine disks, in which securing means the sealing sheets have a shoulder on their inner edge, with which shoulder they bear sealingly against a laterally circumferential projection of the turbine disk. In order to secure the sealing sheets in their final installation position, in each case one closure element is required which, arranged in a recess of the sealing sheet, is inserted at the same time as said sealing sheet into the turbine disk groove. Subsequently, the closure element is removed from the recess and displaced along the turbine disk groove, said closure element then locking the sealing sheet radially and axially onto the turbine disk. In order to secure the closure piece against a displacement in the circumferential direction, its pointer is bent in between two cams which are provided on the sealing sheet. Overall, however, the simultaneous insertion of the sealing sheet and closure element is not easy to install.